docs: def set_dhw_on(self, until=None):
          """Set DHW to on, either indefinitely, or until a specified time.
  
          When On, the DHW controller will work to keep its target temperature
          at/above its target temperature.  After the specified time, it will
          revert to its scheduled behaviour.
          """
  
          time_until = None if until is None else until.strftime(
              '%Y-%m-%dT%H:%M:%SZ')
  
          self._set_dhw(status="Hold", mode="DHWOn", next_time=time_until)